Installing a rainwater tank in New Zealand is a great way to reduce your water bill and improve your home's resilience — but whether you can do it yourself depends on exactly what you're connecting and how. Some parts of the job are perfectly legal for a homeowner to tackle; others are restricted plumbing work that must be carried out by a licensed professional.
What You Can Generally Do Yourself
As a homeowner, you're typically allowed to:
- Position and install the tank itself — placing a freestanding tank on a prepared base is generally not restricted work.
- Set up basic rainwater collection — connecting downpipes to a tank for garden irrigation or outdoor use (not connected to your home's plumbing system) is usually something you can do yourself.
- Install a simple gravity-fed tap on the tank for garden use.
- Prepare the site — levelling ground, laying a concrete pad or compacted gravel base, and ensuring the tank is stable and secure.
Always check your tank manufacturer's installation guide, as improper base preparation can void warranties and cause structural issues.
What Is Restricted Work — and Why It Matters
Under the Plumbers, Gasfitters and Drainlayers Act 2006, any connection of a rainwater tank to your home's internal plumbing system is restricted plumbing work. This includes:
- Connecting the tank to supply your house with water (toilets, laundry, hot water, etc.)
- Installing pumps that feed into the household water supply
- Any cross-connection work between the rainwater system and the mains supply
- Installing backflow prevention devices (required by the NZ Building Code)
If you carry out restricted work without a licence, you could face fines, your home insurance may be voided, and you could create serious health and safety risks for your household.
NZ Building Code Requirements
Rainwater used inside the home must comply with NZ Building Code Clause G12 (Water Supplies). Key requirements include:
- Backflow prevention — to ensure rainwater cannot contaminate the mains supply. This is non-negotiable and must be installed by a licensed plumber.
- Water quality — if rainwater is used for drinking, cooking, or bathing, it must be treated to a safe standard. First-flush diverters, filters, and UV treatment systems are commonly required.
- Overflow and drainage — tank overflows must be directed safely away from foundations and neighbouring properties, in line with Clause E1 (Surface Water).
BRANZ has useful guidance on rainwater collection systems and water quality considerations for NZ homes.
Do You Need a Building Consent?
This is where things can get a little complex. Whether you need a building consent depends on your local council and the specifics of your installation.
- A standalone tank used only for garden irrigation may fall under Schedule 1 exemptions of the Building Act 2004 — meaning no consent is required.
- Connecting a tank to your home's plumbing system will almost certainly require a building consent and a plumbing permit.
- Some councils have specific rules about tank size, placement near boundaries, and stormwater connections.
Always check with your local council before starting work. Don't assume an exemption applies — getting this wrong can cause problems when you sell your home or make an insurance claim. You can find general guidance at MBIE Building Performance.
Choosing the Right Tank
NZ has a wide range of polyethylene and corrugated steel rainwater tanks available. When choosing, consider:
| Factor | What to Look For |
|---|---|
| Capacity | Match to your roof catchment area and intended use |
| Material | Food-grade polyethylene for potable use; UV-stabilised |
| Footprint | Slimline tanks suit smaller sections |
| Inlet/outlet fittings | Ensure compatibility with your downpipe size |
| Overflow | Must be included and directed safely |
Tanks and fittings are available from suppliers like Bunnings and Mitre 10, as well as specialist water tank suppliers around NZ.
Healthy Homes and Rental Properties
If you're a landlord, note that rainwater systems used as the primary water supply in rental properties must meet Tenancy Services Healthy Homes standards for water supply. Always ensure the system is compliant and maintained.
Safety Tips
- Never cross-connect rainwater and mains water supplies — this is a serious public health risk and is illegal without proper backflow prevention.
- Keep tank lids secure to prevent mosquito breeding and contamination.
- Regularly clean gutters, first-flush diverters, and filters.
- If using rainwater for drinking, have it tested periodically.
- Ensure the tank base can handle the full weight of water — 1,000 litres weighs 1 tonne.
When to Call a Professional
You must use a licensed plumber (registered with the Plumbers, Gasfitters and Drainlayers Board) for any connection of your rainwater tank to the household plumbing system, backflow prevention installation, and pump connections. A licensed plumber will also be able to advise on consent requirements and ensure the work is signed off correctly with a Certificate of Compliance.
For the full installation — from site prep through to a compliant, connected system — it's worth getting a qualified local plumber involved from the start. You can find experienced plumbers in your area on tradedirectory.co.nz.